For gray levels, a pixel can be represented by 8 bits. Total bits for this image is 256*256*8. so the compression ratio will be 256*256*8/16384 =32. 32 option is not here. For photographic images, Compression Ratio is usually below 2 for lossless, but can reach over 10 for lossy compression.
The option (b) may be the right option. I am not sure.